A Complete Example

• What can go wrong?
  • File might not exist
  • File might have data in wrong format
• Who can detect the faults?
  • FileReader constructor will throw an exception when file does not exist
  • Methods that process input need to throw exception if they find error in data format
• What exceptions can be thrown?
  • FileNotFoundException can be thrown by FileReader constructor
  • IOException can be thrown by close method of FileReader
  • BadDataException, a custom checked exception class
• Who can remedy the faults that the exceptions report?
  • Only the main method of DataSetTester program interacts with user
    • Catches exceptions
    • Prints appropriate error messages
    • Gives user another chance to enter a correct file